1. Field of the Invention
The present invention relates to a mobile station position detection method and a system for detecting a position of a person or object who or which carries a mobile station in wireless radiocommunications and a radiocommunication system based thereupon, which are capable of accomplishing the detection of the position of the mobile station with a high accuracy.
2. Description of the Prior Art
In wireless communication fields such as portable radio telephone systems and personal handy-phone systems (PHS), a radio wave strength (an electric field strength) level at reception varies in accordance with the distance from a base station. This signifies that the detection of the strength levels of radio waves picked up from a plurality of base stations in a mobile station side allows the detection of the position of the mobile station, i.e., the position of a person or object who or which carries the mobile station. However, in the case of radio communication systems such as prior portable telephones and PHSs where a plurality. of radio zones constitute a service area, the specification of the present location of a mobile station is limited to within a relatively wide area being the range of a radio zone of a base station which accepted the position registration of the mobile station (the range of a general calling area composed of a plurality of radio zones including the radio zone of the base station which accepted the position registration).
For the accurate detection of the location of the mobile station, for example, in the xe2x80x9cMobile Station Position Detection Methodxe2x80x9d disclosed in Japanese Unexamined Patent Publication No. 2-44929, applying the fact that the radio zones of a plurality of base stations overlap with each other, the present location of the mobile station is specified to a smaller area than the radio zone of one base station on the basis of the mobile station reception radio strength levels from the plurality of base stations and the electric field strength map in the radio zone of each of the base stations. The outline of the typical arrangement of the position detection method disclosed in Japanese Unexamined Patent Publication No. 2-44929 will be described hereinbelow with reference to FIG. 20.
A radiocommunication system, introducing this prior mobile station position detection method, as shown in FIG. 20, comprises base stations 2802, 2803, 2804 respectively having radio zones 2805, 2806, 2807, a mobile station 2801 existing in these radio zones, a mobile communication control station 2808 for taking charge of control of communications between the base stations or between the base stations and a wire network, and a position information center 2809 for detecting the position of the mobile station 2801 on the basis of the information attainable through the mobile communication control station 2808. The positional information center 2809 is composed of a positional information transmission and reception unit 2810 for collecting information about reception radio strengths of the respective base stations 2802, 2803, 2804 and an electric field strength map 2811 indicative of the electric field strength distribution of the respective radio zones 2805, 2806, 2807.
The mobile station 2801 stands in a spot at which the radio zones 2805, 2806, 2807 of the plurality of base stations 2802, 2803, 2804 overlap with each other and, hence, can receive radio waves transmitted from the base stations 2802, 2803, 2804. If the mobile station 2801 is not in a connected communication state with a specific base station, the mobile station 2801 is capable of receiving radio signals (for example, information including identifiers of the base stations, intermittently transmitted through control channels) from these base stations 2802, 2803, 2804.
When receiving the radio signals transmitted from the base stations 2802, 2803, 2804, the mobile station 2801 measures the strength levels of these radio signals and transmits the reception radio strengths on the respective base stations 2802, 2803, 2804, together with the base station identifiers, through any one of the base stations 2802, 2803, 2804 to the mobile communication control station 2808. The mobile communication control station 2808 communicates the reception radio strengths on the base stations 2802, 2803, 2804 from the mobile station 2801, toward the positional information transmission and reception unit 2810 of the positional information center 2809. The positional information center 2810 stores the electric field strength map 2811 made in advance and representative of the electric field strength distribution in the radio zones of all the base stations, which the mobile communication control station 2808 manages, in the form of field strength contours. In the positional information transmission and reception unit 2810, on the basis of the electric field strength map 2811 on the base stations 2802, 2803, 2804, the field strength contours corresponding to the reception radio strength levels on the base stations 2802, 2803, 2804 from the mobile station 2810 are drawn to attain an area in which the respective field strength contours intersect with each other. This area is a spot detected as the position at which the mobile station exists. Thus, the position detection method disclosed in Japanese Unexamined Patent Publication No. 2-44929 can specify the position of the mobile station to within a smaller range than the radio zone of one base station, thereby realizing a position detection with a high accuracy.
However, for applying the position detection method disclosed in Japanese Unexamined Patent Publication No. 2-44929, it is necessary that the electric field strength map on the base stations constituting a service area is known in advance. In general, the electric field strength distribution on some base station is affected by various obstacles or reflectors (roads, houses, buildings and others in the outdoor places, and floors, ceilings, partitions and other in the indoor places) which exist within its radio zone, great difficulty is encountered to predict this electric field strength map from the radio wave characteristic of the base station, and therefore, detailed measurements using a field strength meter or the like are required in order to find the electric field strength map at every base station. In fact, for example, in FIG. 4 (p. 773 (61)) of xe2x80x9cArrangement of PHS Terminalsxe2x80x9d written by Nakamura, Akazawa, Oka and Mizutori in the Document xe2x80x9cNTT RandDxe2x80x9d No. 9 (Vol. 44) 1995, pp. 769 (57)-pp. 774 (62), there has been shown an electric field strength distribution on a PHS base station in a house. Referring to this, the PHS electric field strength distribution obviously assumes an extremely complicated configuration in a room.
For this reason, for improving the position detection accuracy in this method, a more accurate electric field strength map is required to be obtained through measurements. However, the measurements of the electric field strength distributions on all the base stations require exceedingly expensive labor. Accordingly, the detection of the position of the mobile station with a higher accuracy than that due to the radio zone of one base station is approximately impossible or extremely difficult if taking into consideration the exceedingly expensive labor required for the production of the electric field strength map.
Moreover, for eliminating the above-mentioned problem, the report xe2x80x9cStudy on Mobile Station Position Detection Based upon Reception Level Informationxe2x80x9d Electronic Information Communication Scientific Society Autumn Meeting B-269 (1993) presents a method to specify the present location of a mobile station to within a range smaller than a radio zone of one base station through the use of mapping table of reception radio strength levels from a plurality of base stations received by the mobile station and a position (X, Y) of the mobile station by using the fact that the radio zones of the plurality of base stations overlap with each other. This position detection method will be described hereinbelow with reference to FIG. 21. For the basic data for the position detection, reception radio strength levels from a plurality of base stations are measured at points within a service area, and the positions (X, Y) of the measuring points and the radio strength levels (E1, E2, E3, E4 and E5) from base stations BS1, BS2, BS3, BS4 and BS5 received there are made to correspond to each other and accumulated in a database in a center processing section in advance. In the case of detecting the position of the mobile station, radio strength levels (E1xe2x80x2, E2xe2x80x2, E3xe2x80x2, E4xe2x80x2 and E5xe2x80x2) received from the plurality of base stations are transmitted to a center to be checked with the closest radio strength levels of the radio strength levels accumulated in the database of the center to estimate the position (Xxe2x80x2, Yxe2x80x2) of the mobile station. Thus, the position detection method described in the report xe2x80x9cStudy on Mobile Station Position Detection Based upon Reception Level Informationxe2x80x9d can estimate the position of the mobile station within a range smaller than the radio zone of one base station.
There is a problem which arises with this position detection method, however, in that since the estimation of the position is made in the manner that the closest reception radio strength data is retrieved in the position database, the estimated position is limited to the actual measuring points. In addition, in general the recognition of a place is made with a floor or room number in the case of an indoor place and with a building or inherent area name in the case of an outdoor place, and the recognition using the coordinates is inconvenient in many cases. Accordingly, in the case of detecting the position expressed with such a discrete value, it is considered that this position detection method is made such that, for example, the correspondence between room numbers and coordinates is prepared in advance and the estimated position of the mobile station is converted into a room number. However, the the position estimated in terms of a room greatly differs from the position estimated with respect to the vicinity of the boundary between rooms, and hence, even if the closest point is specified on the reception radio strength levels, the error rate increases so that difficulty is encountered to know the degree of the reliability of the position detection.
The present invention has been developed in order to eliminate the above-mentioned problems, and it is therefore an object of the present invention to provide a radio mobile station position detection method which is capable of accurately and simply finding the position of a mobile station to promote the reliability of the position detection and a radiocommunication system based upon the aforesaid position detection method of the mobile station.
In a position detection method of a mobile station according to the present invention, the mobile station measures the reception radio wave (electric field) strength levels from a plurality of base stations at a measuring point to convey the measurement results through a base station to a control station, while the control station uses a neural network to learn a correlation between the reception radio strength levels and the position of the mobile station on the basis of the measurement results at a plurality of measuring points and the positional data at the measuring points. Further, when the mobile station sends the measurement results of the reception radio strengths from the plurality of base stations measured at the plurality of measuring points, the control station estimates the position of the mobile station bearing the measurement results on the correlation between the reception radio strength levels and the positions of the mobile station obtained through the learning.
In addition, the control station communicates the structure of the neural network experiencing the learning to the mobile station, so that the mobile station measures the reception radio strength levels from the plurality of base stations to detect its own present position on the basis of the measurement results. Further, the plurality of base stations measure the reception ratio strength level from the mobile station at a measuring point and conveys the measurement results to the control station which in turn, learns the correlation between the reception radio strength level at each of the base stations and the position of the mobile station through the neural network on the basis of the measurement result in each of the respective base stations and the positional data at the measuring point. When the respective base stations transmit the measurement results on the reception radio strength levels of the radio wave emitted from the mobile station at a given point, the control station estimates the position of the mobile station on the basis of the correlation it learns.
Furthermore, in a wireless radiocommunication system according to the present invention, a mobile station is equipped with radio strength measuring means for measuring the reception radio strength levels from a plurality. of base stations, whereas a control station is provided with position input means for accepting or inputting the position of a measuring point, position learning processing means for learning, through a neural network, the correlation between the reception radio strength levels measured by the mobile station at a plurality of measuring points and the position of the measuring point inputted from the position inputting means, and position estimation processing means for, using the reception radio strength levels from the plurality of base stations measured by the mobile station at a given point, estimating the position of the mobile station at the measuring time on the basis of the correlation the position learning processing means learns.
In addition, the mobile station is equipped with learning result storage means for storing parameters of the neural network conveyed from the control station and position calculation means for constructing a neural network through the use of the parameters to detect its own position. Further, each of the base stations is provided with radio strength measuring means while the control station includes position input means for accepting the position of the measuring point, position learning processing means for learning, through a neural network, the correlation between the reception radio strength levels from the mobile station measured by the respective base stations and the position of the measuring point, and position estimating means for estimating the position of the mobile station on the basis of the reception radio strength levels from the mobile station measured by the respective base stations.
Thus, according to this invention, since the detection of the position of the mobile station is accomplished through the learning by the neural network, the measuring work at the preparation stage is satisfied with the measurements of the reception radio strength levels at a typical measuring point, with the result that the working quantity can be reduced in the preparation stage.
In accordance with an aspect of the present invention, in a position detection method for detecting a mobile station in a wireless radiocommunication system including the mobile station, base stations and a control station, the mobile station measures the reception radio strength levels from a plurality of base stations at a measuring point and communicates the measurement results through the base station to the control station which in turn, learns, through a neural network, the correlation between the reception radio strength levels and the position of the mobile station on the basis of the measurement results at a plurality of measuring points and the positional data of the measuring points, and when the mobile station conveys the measurement results of the reception radio strength levels from the plurality of base stations measured at a given point through the base station to the control station, the control station estimates the position of the mobile station producing the measuring results on the basis of the correlation between the reception radio strength levels and the positions of the mobile station attained through the learning. Accordingly, owing to the learning of the correlation between the positions of the mobile station and the reception radio strength levels from the plurality of base stations at that point, the estimation of the position of the mobile station is possible on the basis of the electric field strength levels of the plurality of base stations the mobile station receives at the given point.
Furthermore, another aspect of this invention is that the measuring points are determined in advance and each of the mobile stations measures the reception radio strength levels from a plurality of base stations at its own measuring point so that the learning is made of the correlation between the reception radio strength levels measured at the measuring point predetermined in position beforehand and the position of the measuring point. Still further, the measuring point is set to a place at which a charger for charging the mobile station stands so that the reception radio strength levels are measured and reported to the control station while the mobile station is located on the charger known in position for the charging. The control station learns the aforesaid correlation on the basis of the positional data of the charger and the reported reception radio strength levels.
Moreover, a further aspect of this invention is that the mobile station communicates the positional data of a measuring point and the reception radio strength levels from a plurality of base stations measured at the measuring point through the base station to a control station. The mobile station measures the reception radio strength levels from the plurality of base stations and inputs its own position through the input by the user or through a position detection unit to report both the measured reception radio strength levels and its own position to the control station. The control station learns the aforesaid correlation on the basis of the position of the mobile station and the reception radio strength levels at that point.
In addition, a further aspect of this invention is that the mobile station measures the reception radio strength levels from a plurality of base stations plural times at the same measuring point or an arbitrary point and statistically processes the plurality of measurement values to output the obtained single value as a final measurement result, which can enhance the accuracy of the measurement result in the mobile station. Further, when the mobile station conveys the measurement results of the reception radio strength levels from a plurality of base stations measured at an arbitrary point through the base station to the control station, the control station estimates the position of the mobile station corresponding to the measurement results on the basis of the correlation between the reception radio strength levels and the positions of the mobile station obtained through the learning and communicates the estimation result to the mobile station. Accordingly, the user who carries the mobile station can find his own position through the inquiry to the control station.
Furthermore, a further aspect of this invention is that, when a mobile station inquires for the position of a different mobile station, a control station gives instructions to the different mobile station to measure the reception radio strength levels from a plurality of base stations and to report them, and in response to the report of the measurement results, the control section estimates the position of the different mobile station on the basis of the measurement results and conveys the estimation result to the mobile station which made the inquiry therefor. Accordingly, the user who carries the mobile station can find the position of a person carrying the different mobile station by the inquiry to the control station.
Still further, a control station successively stores the estimation results of the position of a mobile station, and when estimating the position of the mobile station on the basis of a new measurement result, the control station decides, on the basis of the past positions of the mobile station, whether or not the estimated position of the mobile station is appropriate. If not appropriate, the control station gives instructions to the mobile station to again make the measurements. Thus, the reliability of the estimation results can improve through this procedure. Besides, the mobile station measures the reception radio strength levels from a plurality of base stations at a given equal time interval and conveys the measurement results through the base station to the control station. The control station obtains the position of the mobile station at the equal time interval on the basis of the measurement results and stores them in time series, with the result that it is possible to more accurately judge the appropriateness of the position of the mobile station newly estimated.
In addition, a further aspect of this invention is that a control station converts the reception radio strength level transmitted from a mobile station into a theoretical distance between the mobile station and a base station and learns, through a neural network, the correlation between this theoretical distance and the position of the mobile station, so that the learning processing becomes easy and the improvement of the learning accuracy becomes possible.
Moreover, in a position detection method for detecting the position of a mobile station in a wireless radiocommunication system equipped with the mobile station, a plurality of base stations and a control station according to this invention, the mobile station measures the reception radio strength levels from the plurality of base stations at a measuring point and communicates the measurement results through the base station to the control station, which in turn, learns, through a neural network, the correlation between the reception radio strength levels and the positions of the mobile station on the basis of the measurement results at a plurality of measuring points and the positional data of the measurement points and further conveys the parameters of the neural network obtained through the learning to the mobile station, while the mobile station constructs a neural network through the use of the parameters and detects its own position on the basis of the reception radio strength levels from the plurality of base stations measured at an arbitrary point through the use of the constructed neural network. With this method, the mobile station can detect its own position without the inquiry to the control station.
In addition, a control station learns, through a neural network, the correlation between the reception radio strength levels and areas such as a room and a zone having an extension in which a mobile station stands, with the result that the room or zone in which a person carrying the mobile station exists is detectable and it is possible to present a plurality of places as the candidates for the person""s whereabouts.
Furthermore, in a position detection method for detecting the position of a mobile station in a wireless radiocommunication system equipped with the mobile station, base stations and a control station, each of the base stations measures the reception strength level of a radio wave emitted from the mobile station standing at a measuring point and conveys the measurement result to the control station, while the control station learns, through a neural network, the correlation between the reception radio strength levels and the positions of the mobile station on the basis of the measurement results at a plurality of measuring points and the positional data of the measuring points, and when each of the base stations measures the reception radio strength level of a radio wave emitted from the mobile station standing at an arbitrary point and conveys the measurement result to the control station, the control station estimates the position of the mobile station bearing the measurement results on the basis of the correlation between the reception radio strength levels and the positions of the mobile station obtained through the learning. Thus, it is easily applicable to a system such as a mobile radio telephone system and PHS where a plurality of base stations measures the radio wave transmitted from a mobile station.
Moreover, in a wireless radiocommunication system equipped with a mobile station, base stations and a control station and allowing the control station to detect the position of the mobile station, the mobile station is equipped with radio strength measuring means for measuring reception radio strength levels from a plurality of base stations, while the control station is provided with position input means for receiving the position of a measuring point, a position learning processing means for learning, through a neural network, the correlation between the reception radio strength levels by the mobile station at a plurality of measuring points and the positions of the measuring points inputted through the position input means, and position estimation processing means for estimating, on the basis of the reception radio strength levels from the plurality of base stations measured by the mobile station at an arbitrary position, the position of the mobile station at the measuring time through the use of the correlation the position learning processing means learn. Thus, the detection method based upon the learning by the neural network is practicable for the position detection of the mobile station.
Furthermore, a mobile station is equipped with radio strength measuring means for measuring the reception radio strength levels from a plurality of base stations, whereas a control station is provided with position storage means for storing the position of each of measuring points and an identifier of the mobile station corresponding to the measuring point, position learning processing means for learning, through a neural network, the correlation between the reception radio strength level measured at the measuring point by the mobile station and the position of the measuring point stored in the position storage means, position estimation processing means for estimating the position of the mobile station at the measuring time on the basis of the reception radio strength levels from the plurality of base stations measured by the mobile station at an arbitrary point through the use of the correlation the position learning processing means learns. This system can adopt a position detection method in which the learning is conducted using the reception radio strength level measured by a predetermined mobile station at a predetermined measuring point.
In addition, for charging a mobile station is located at a measuring point, so that the mobile station reports the reception radio strength level measured during the charging to a control station whereas the control station learns using the reception radio strength level and the position of the charger known in advance. Further, at the position of the measuring point, there are situated a learning data collector provided with radio strength measuring means for measuring reception radio strength levels from a plurality of base stations and transmission and reception means for transmitting the measured radio strength levels through the base station to a control station and further for receiving a control signal from the control station, with the result that the control station can learn using the reception radio strength levels sent from the learning data collector at regular intervals or in accordance with commands.
Furthermore, a mobile station is equipped with radio strength measuring means for measuring the reception radio strength levels from a plurality of base stations and position input means for taking in its own position information, whereas a control station is provided with position learning processing means for learning, through a neural network, the correlation between the reception radio strength levels measured by the radio strength measuring means of the mobile station and the position of the mobile station at the measuring point inputted from the input means and for storing the learned correlation therebetween, and position estimation processing means for estimating the position of the mobile station at the measuring time on the basis of the reception radio strength levels from the plurality of base stations measured by the mobile station at an arbitrary point through the use of the correlation the position learning processing means learns. This system can realize a position detection method in which the mobile station takes in its own position through the operation by the user or through a different position detection device in addition to the measured reception radio strength levels and the control station learns using these data.
Furthermore, the control station is equipped with radio strength report requesting means for transmitting a radio strength report requesting message to the mobile station so that the mobile station measures the reception radio strength levels from the plurality of base stations and reports the measurement results thereto. Accordingly, the control station can request the radio strength measurement data from an arbitrary mobile station when necessary. Still further, the mobile station is equipped with self mobile station position inquiry means for issuing a measurement request for radio strength levels to the radio strength measuring means, and when receiving the reception radio strength levels measured by the radio strength measuring means, the control station estimates the position of the mobile station and informs the mobile station of the estimation result. In this system, the user of the mobile station can operate the self mobile station position inquiry means to inquire to the control station for its own present position. In addition, the mobile station is provided with different mobile station position inquiry means for transmitting a request for the inquiry for the position of a different mobile station to the control station, and when the control station receives this request, the radio strength report requesting means issues a radio strength report request message to the different mobile station whose position is inquired and, in response to the report on the measurement result of the radio strength levels from the different mobile station, the control station estimates the position of the different mobile station on the basis of measurement result to inform the mobile station, which made the inquiry, of the estimation result. According to this system, the user who carries the mobile station can operate the different mobile station position inquiry means to inquire to the control station for the position of the person who carries the different mobile station.
Moreover, the control station is equipped with position accumulation means for accumulating the information on the positions of the mobile station estimated in the position estimation processing means in time series and history decision means for deciding, on the basis of the transition of the position of the mobile station with time accumulated in the position accumulation means, whether the position of the mobile station estimated by the position estimation processing means is appropriate or not. If the history decision means makes a decision to that it is not appropriate, the radio strength report requesting means transmits the radio strength report requiring message to the mobile station. According to this system, in the case that an inproper estimation result arises due to a large variation of the electric field distribution of the base station, the measurement is resumed, thus enhancing the accuracy of the estimation result.
In addition, the mobile station is equipped with at least two frequency synthesizers, and even if one frequency synthesizer synchronizes with a communication carrier at the call, the radio strength measuring means measures the radio strength levels from a plurality of base stations through the use of the other frequency synthesizer. Thus, the mobile station can perform the measurements of the reception radio radio strength levels irrespective of the call. Further, the control station is provided with distance calculation means for calculating the distance between the mobile station and each of the base stations as a function of of the reception radio strength levels from a plurality of base stations measured by the mobile station through the use of a theoretical electric field strength distance characteristic obtainable from the outputs and frequencies of the base stations, and the position learning processing means learn, through a neural network, the correlation between the calculated distance and the position of the measuring point. This system permits the position estimation with a high accuracy through the use of the calculated theoretical distance for the learning.
Furthermore, the mobile station is equipped with learning result storage means for storing the parameters for a neural network conveyed from the control station and position calculation means for constructing a neural network using the parameters stored in the learning result storage means to detect its own position on the basis of the reception radio strength levels from a plurality of base stations measured at an arbitrary point through the use of the constructed neural network. This system can adopt the above-mentioned position detection method in which the mobile station detects its own position without the inquiry to the control station. Still further, the control station learns the correlation between the reception radio strength levels and the area in which the mobile station stands, through a neural network including nodes of an input layer accepting the reception radio strength levels from a plurality of base stations and nodes of an output layer corresponding in number to the areas defining the range of an object under detection such as a room and a zone. This system can conduct the above-mentioned position detection method which detects the room or zone where a person carrying the mobile station exists or presents a plurality of places as the candidates for the person""s whereabouts.
Moreover, in a wireless radiocommunication system equipped with a mobile station, base stations and a control station and made such that the control station detects the position of the mobile station, each of the base stations is provided with radio strength measuring means for measuring the reception radio strength level from the mobile station, while the control station is equipped with position input means for accepting the position of a measuring point, position learning processing means for learning, through a neural network, the correlation between the reception radio strength level of the radio wave emitted from the mobile station at the measuring point and measured by the base station and the position of the measuring point inputted through the position input means, and position estimation processing means for estimating the position of the mobile station on the basis of the reception radio strength level from the mobile station measured by each of the base stations through the use of the correlation the position learning processing means learns. This system can introduce the above-mentioned position detection method in which a plurality of base stations measure the radio wave from the mobile station to detect the position of the mobile station.
In addition, in a mobile station position detection method according to this invention, the radio strength levels from a plurality of base stations at a measuring point within a service area are measured plural times and accumulated in a radio strength data storage section which makes a corresponding relation (mapping) between the reception radio strength levels and a position expressible with a continuous value such as coordinate, and the reception radio strength levels in the radio strength data storage section are compared with reception radio strength levels at a position detecting point at the time of the position detection, and when a position detection section estimates the position of the mobile station by introducing such a statistic method as to calculate a weighted mean of a plurality of radio strength data that the radio strength level comparison result shows a small error. Accordingly, the estimated position is not limited to the actual measurement point and the position of the mobile station can be estimated within a range smaller than a distance between the measuring points.
Furthermore, of the reception radio strength levels and the position coordinates accumulated in a radio strength data storage section, the position coordinates are accumulated as a position expressible with a discrete value, and the radio strength data in the radio strength data storage section are compared with the reception radio strength levels at the position detection so that the position of the mobile station is estimated by employing a statistic method in which, for example, a position detection control section makes a majority decision using a plurality of radio strength data that the radio strength comparison result shows a small error, and the degree of the reliability of the position detection is found through, for example, a statistic method to use the rate of the estimated position to a plurality of extracted radio strength data.
According to this invention, a wireless radiocommunication system which performs radiocommunications between a mobile station and a base station is equipped with radio strength data storage section for retaining positional information on a plurality of measuring points expressible with continuous values and radio strength data including reception radio strength levels from a plurality of base stations at the respective measuring points, a position detection section having means for comparing the radio strength data in the radio strength data storage section with radio strength levels at a position detecting point to estimate the position, an error radio strength data storage section for holding a plurality of radio strength data involving a small error on the comparison in the position detection section, and the position detection section performs the position detection using the plurality of radio strength data in the error radio strength data storage section. Thus, the estimated position is not limited to the actual measuring point but the position can be estimated with a range smaller than the interval between the measuring points.
Furthermore, according to this invention, a wireless radiocommunication system which performs radiocommunications between a mobile station and a base station is equipped with radio strength data storage section for retaining positional information on a plurality of measuring points expressible with discrete values and radio strength data including reception radio strength levels from a plurality of base stations at the respective measuring points, a position detection section having means for comparing the radio strength data in the radio strength data storage section with radio strength levels at a position detecting point to estimate the position, an error radio strength data storage section for holding a plurality of radio strength data which produce a small error in the comparison in the position detection section, and the position detection section performs the position detection expressible with the discrete values, using the plurality of radio strength data in the error radio strength data storage section. At the position detection, the radio strength data in the radio strength storage section is compared with the reception radio strength levels taken for the position detection, and a position detection control section estimates the position by, for example, employing a statistic method to make a majority decision on the plurality of radio strength data in the error radio strength data storage section which make a small comparison error and further estimates the degree of the reliability of the obtained position by, for example, employing a statistic method to calculate the rate of the estimated position to the plurality of radio strength data.
In addition to these arrangements, a position detection knowledge section is provided which has a knowledge on a person carrying the mobile station and an action rule or schedule of that person, and the position detection section carries out the position detection through the use of the plurality of radio strength data in the error radio strength data storage section and the knowledge in the position detection knowledge section. Because of using the knowledge on a person and an action rule and schedule of that person at the position estimation, it is possible to remove data with a low possibility of movements such as the inhibition of entry into a room but to select data with a high possibility of movements, with the result that the position detection can improve in accuracy.
Furthermore, a position detection knowledge section is provided which has knowledge on the relationship between a plurality of positions expressible with discrete values, and the position detection section conducts the position detection using a plurality of radio strength data in the error radio strength data storage section and the knowledge in the position detection knowledge section. Through the use of the knowledge on the relationship between the plurality of positions expressible with discrete values, it is possible to exclude, of the plurality of radio strength data held in the error radio strength data storage section, the data remote in connection, and it is possible to decide whether or not it corresponds to the vicinity of the boundary between rooms, thus developing the position detection accuracy.
Still further, the position detection is conducted in such a manner that the number of radio strength data held in the error radio strength data storage section is changed in accordance with the degree of the error between the radio strength levels at the position detecting point and the radio strength data in the radio strength data storage section. Since the number of the radio strength data in the error radio strength data storage section varies in accordance with the degree of the error, the improvement of the position detection accuracy is possible.
Moreover, the position detection section is equipped with a position accumulation section for accumulating short-term positions the position detection section estimates in the past and a history decision section for deciding the appropriateness of the estimated position on the basis of the radio strength data held in the error radio strength data storage section. The appropriateness of the estimated position is judged in a manner that the moving situation is decided on the basis of the latest estimated position of the mobile station in the past and that time and further the present position and the time at that position. If not appropriate, the position detection is again conducted. Since the moving speed or the locus is calculated on the basis of the short-term history to decide the appropriateness of the estimated position, the position detection can improve in accuracy.
In addition, in place of accumulating the short-term positions estimated in the past, a long-term history is established and held by accumulating the past experiences such as the places to which the mobile station has moved in the past and the frequency of the movements in the short terms to decide, on the basis of the past movement experiences of the mobile station, whether the estimated position is appropriate or not. If not appropriate, the position detection is again conducted. Since the appropriateness of the position estimated by the possible movement range of the mobile station on the past experiences of the mobile station is judged from the long-term history, the improvement of the position detection accuracy is possible.